I have a client who recently moved premises. We moved the SBS server and re-configured both internal and external IP addresses. I changed the public IP address in their DNS registrars control panel to point to the new public IP address assigned on the new firewall to their mail server. Mail was flowing within 1 hour. So far so good. After approximately 2 weeks the IP address of the gateway router ended up on a spamhous blocklist. From what I could decipher it looks like it was because there is no reverse DNS PTR record. The DNS registrar has told me I need to do this at the server - I have never had to do that before. I have moved many a server in the past and this is the first time this has happened and I am unsure of what to do. The errors in some NDR's include the name of the service provider who supplied the fibre connection. So, where does the reverse lookup record reside? Is it at the DNS registrar? Or the internet service provider? Or directly on the server? If it's on the server do I create a new reverse DNS zone to match the mx record and the IP address? I appreciate any help with this. The client is trying to send out invitations to their grand opening and as you can imagine they are not pleased.